The present invention relates to a head-arm mechanism making heads move on information areas of a disk as a information storing medium so that the heads record information on the disk and/or reads information from the disk.
For example, a head-arm mechanism applied to a hard disk apparatus shown in FIG. 1, which apparatus uses a hard magnetic disk 1 as an information storing medium, includes a retaining or holding means. The retaining means retains or holds the head-arm during an idle time, in which time such recording and/or reading operation of a magnetic heads 7a, 7b is not performed. Then, the magnetic heads 7a, 7b, each of which heads 7a, 7b is provided on a respective nose end of arms 4a or 4b each of which arms 4a, 4b is respectively provided on top portions of head-arm 4, are retained on a landing zone of the disk. Landing zones 1a provided on each of front and rear surfaces of the disk 1 is located on an inner portion of the disk 1 for the heads 7a, 7b to land thereon, in which zones 1a no information is recorded. The hard magnetic disk 1 is one kind of a magnetic disk that has, for example, such a construction as made of an aluminium base being coated by a magnetic material.
On the base 2 made of die-cast aluminium, the spindle motor 3 for rotating the hard magnetic disk 1 is located, the spindle motor 3 being fixed the disk thereon. On the base 2, the head-arm 4 is also located, the head-arm being supported by the shaft 6 so that the arm can rotate, an axis of the rotation being the shaft. The head-arm is driven by the voice coil motor 5 so as to rotate in the direction designated by the arrow A as shown in FIG. 1.
The heads 7a, 7b respectively access desired tracks on the data areas 1b provided on each of front and rear surface of the disk 1, depending on the rotation of the head-arm 4, so that recording data on the data areas 1b or reading data therefrom during an access time, in which time such recording or reading operation of the heads 7a, 7b are performed is carried out.
Besides the head-arm 4, the coil 5a comprising the voice coil motor 5 and the flexible printed circuit board 8 for wiring to the magnet heads 7a. 7b from the printed circuit board 9 are located. The one end of the flexible printed circuit board 8 is connected electrically and mechanically to the folded portion 9a of the printed circuit board 9, which board 9 being located on the base 2.
The flexible printed circuit board 8 has elasticity so that the board 8 can bend due to the outside force applied thereto. Thus, as shown in FIG. 1, the board 8 is applying an elastic force to a side of the head-arm 4 in the direction designated by the arrow B. Accordingly, if the head-arm 4 is not driven by the voice coil motor 5, the magnetic heads 7a, 7b are moved in the direction of the landing zones 1a of the disk 1 due to the elastic force of the flexible printed circuit board 8 which force being applied to the head-arm 4.
A retaining means comprises the attracted chip 10, magnet 11 and holder 12.
The attracted chip 10 made of iron is fixed to the side of the head-arm 4. In the point on the base 2 near to the shaft 6 and voice coil motor 5, the magnet 11 is provided, which magnet 11 is supported by the holder 12. If the head-arm 4 is not driven by the voice coil motor 5, then to the head-arm 4 is applied the elastic force of the flexible circuit board 8 to rotate the head-arm 4 anti-clockwise so that the heads 7a, 7b respectively reach points on the landing zones 1a. Then the magnet 11 attracts the attracted chip 10 by means of a magnetic force. Thus, the heads 7a, 7b are retained on the landing zones 1a by the retaining means, and this position of the head-arm 4 where the heads 7a, 7b are respectively retained on the zones 1a is called a retained position.
However, in the conventional head-arm mechanism as shown in FIG. 1, the magnet 11 and holder 12 are provided in a position on the base 2 near the voice coil motor 5 and shaft 6. On the other hand, recently, miniaturization of a hard magnetic disk apparatus such as the example shown in FIG. 1, has become necessary. On an area of the base 2 where the disk 1 is located is located the magnet 11 and holder 12, voice coil motor 5, and also printed circuit board 9 and so on.
Here, minimizing of the area of the base 2 is directed to achieve the miniaturization of the hard disk apparatus shown in FIG. 1. Firstly, to improve the degree of freedom regarding the design of the location of parts on the base 2, for example, the arrangement of parts on the base 2 is based on the requirement that the magnet 11 is to be located in a position near the disk 1 that has not been utilized for locating parts yet. However, in the above arrangement, a magnetic field formed by the magnet 11 interferes with data stored in the data areas 1b on the disk so as to destroy the data or so that a signal/noise ratio of the data becomes degraded.
The attracted chip 10 is located in a position on the side of the head-arm 4 near the shaft. There is a distance l.sub.1 as shown in FIG. 1 between the rotational axis of the head-arm 4, which acts as a fulcrum of a lever, and the position of the attracted chip 10, which is a point of application of force on the lever, is relatively short. Thus, in accordance with the well-known principle of the lever, the shorter the distance between the fulcrum and the point of application of force, the smaller the torque applied to the lever resulting from the force applied to the point of application of force.
Therefore, it is necessary to make the magnetic force of the magnet 11 large to ensure the head-arm 4 is retained at the retaining position against the elastic force applied by the flexible printed circuit board 8, or against a vibration applied from the outside to the disk apparatus using the retaining means, if the apparatus is carried by an operator.
However, if the magnetic force of the magnet 11 is made large, the magnetic force may interfere with an operation of the voice coil motor 5.